With reference to the state of the art, different systems for smoothing and polishing metals with free solid bodies (particles) are known. Thus, a great diversity of devices has been used over a time in which mechanical abrasion occurs by using particles not secured on any support, having different geometries and sizes and hardest than the material to be treated. Such devices produce friction of the particles on the parts to be treated thanks to the relative motion they produce between both. These devices consist, for example, of rotating receptacles (drum), vibrating receptacles, or particles blasters.
However, all systems based in direct mechanical abrasion, such as those mentioned above, have the serious defect that they affect the parts with little evenness, meaning that as a given proportionality exists between the pressure exerted by the abrasive (the particles) on the parts and the amount of eroded material, the protruding areas of the parts sustain a wear and rounding off that, in many cases, is excessive. In addition, the global mechanical energy delivered by these systems causes damage to the parts in many cases due to strokes and deformations for excessive stresses. On the other hand, systems based on mechanical abrasion produce surfaces on metal parts having plastic deformation and unavoidably occlude non-trivial amounts of foreign matters, making such treatment unsuitable in many cases due to contamination of the surface layers of the material.
Likewise, polishing systems by galvanic treatments are known, in which the metal parts to be treated are immersed in an electrolyte liquid and without solid particles as anodes, known as electropolishing. These methods have the advantage that they produce surfaces free of the surface contamination of the exclusively mechanical abrasive methods above disclosed. Now then, the levelling effect on the roughness of the order of more than a few microns that is achieved is, in many cases, insufficient and therefore the treatments are mostly used as finish of prior mechanical abrasion methods.
In addition, there exists galvanic methods in which the metal parts to be treated are immerged in an electrolyte liquid containing solid bodies (particles) that freely move within it. The electrolytes developed for the methods produce anodic layers thicker than in the case of the galvanic methods without particles, so that when the particles contained mechanically interact with the anodic layer, up to one-millimeter effective smoothing occurs on the roughness. However, as well in one case as in the other, the galvanic methods used up to now produce, in many cases, defects in the shape of pinholes or of stepped surfaces related to the structure and crystalline composition of the metal to be treated, their use remaining, in many cases, restrained to parts that, because of their composition (alloy) and molding treatment and forming, empirically proved that they can be treated without showing the defects in an unacceptable way.